const fp = require('lodash/fp');

const cars = [
  {
      name: 'Ferrari FF', horsepower: 660, dollar_value: 700000, in_stock: true
  },
  {
      name: 'Spyker C12 Zagato', horsepower: 650, dollar_value: 648000, in_stock: false
  },
  {
      name: 'Jaguar XKR-S', horsepower: 550, dollar_value: 132000, in_stock: false
  },
  {
      name: 'Audi R8', horsepower: 525, dollar_value: 114200, in_stock: false
  },
  {
      name: 'Aston Martin One-77', horsepower: 750, dollar_value: 1850000, in_stock: true
  },
  {
      name: 'Pagani Huayra', horsepower: 700, dollar_value: 1300000, in_stock: false
  }
]
// 练习1
const fn = fp.flowRight(fp.prop('in_stock'), fp.last)
console.log('练习1', fn(cars));
// 练习2
const fnName = fp.flowRight(fp.prop('name'), fp.first)
console.log('练习2', fnName(cars));

// 练习3
let _average = function (xs) {
  return fp.reduce(fp.add, 0, xs) / xs.length;
}
// 改造前
// let averageDollarValue = function (cars) {
//   let dollar_values = fp.map(function(car) {
//     return car.dollar_value
//   }, cars)
//   return _average(dollar_values)
// }
// let averageDollarValue = function (cars) {
//   return fp.map(function(car) {
//     return car.dollar_value;
//   }, cars);
// }
let average = fp.flowRight(_average, fp.map(car => car.dollar_value));
// let average = fp.flowRight(_average, averageDollarValue);
console.log('练习3', average(cars));

// 练习4
let _underscore = fp.replace(/\W+/g, '_')
const sanitizeNames = fp.flowRight(fp.map(_underscore), fp.map(fp.toLower), fp.map(car => car.name))
console.log(sanitizeNames(cars));